The invention relates to an apparatus for applying liquid, pasty or plastic substances, particularly thermoplastic substances, to a substrate with a device for melting these substances and a feed head for transferring the melted substances to the substrate via at least one nozzle orifice.
Such apparatuses are e.g. used in fixing insert technology, in which a thermoplastic adhesive is applied to a textile substrate and the latter is joined to a further substrate. However, such apparatuses are also used for transferring substances to paper or similar carrier substrates.
Conventionally the substance is delivered in lump or granule form and must be melted prior to application. This usually takes place in a separate container from which then the melted substance is brought via a pump to the feed head. This pump has proved disadvantageous in that it destroys the high molecular chains from which the substances are generally formed In addition, melting takes a considerable time, because generally the entire content of the melting container must first be brought into a fluid state prior to the start of application.
Further disadvantages of known apparatuses relate to the feed head and the transfer of the substance to the substrate. In many cases nowadays use is made of a beamlike feed head, upstream of whose nozzle orifice rotates a metal cylinder, cf.DE-OS 32 48 889. The substances to be applied to the substrate through the metal cylinder Perforations often only hang within a gap region within the perforations as a result of the short contact time between substrate and metal cylinder and are not absorbed by the substrate. In order to improve this, the substance could e.g. be heated more and therefore further liquefied, but this would lead to it penetrating too deeply into the substrate and might even puncture the latter.